Effect of receptor occupancy on [3H]dexamethasone binding to circulating leukocytes

To determine the effect of steroid occupancy of the glucocorticoid receptor on the measurement of total receptor concentration using Scatchard plot of [3H]dexamethasone (Dex) binding to circulating leukocytes, leukocytes were incubated with 10(-7)M cortisol or 10(-9)M Dex prior to [3H]Dex binding study. Total binding capacity calculated from Scatchard plot analysis of [3H]Dex binding was not significantly reduced after pre-incubation with cortisol. However, total binding capacity was significantly lower after pre-incubation with Dex. These data suggest that total glucocorticoid receptor concentration can be measured from a 3 h incubation of leukocytes obtained from untreated patients.